This invention relates in general to vehicles and, in particular, to device to enhance wheel adhesion.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to a device and method for enhancing the adhesion qualities of vehicle wheels through the use of a plurality of embedded members having exposed high frictional surfaces, which are capable of automatically being caused to attain frictional contact with a wheel bearing surface in response to slippage. Under normal conditions where enhanced friction is not needed, the embedded members lie in a relative retracted position from which they may respond to slippage conditions as needed.
In many forms of vehicles, attainment of suitable traction of wheels under a wide range of varying conditions has been a long felt problem. In particular, railroad wheels have traditionally been subject to slippage during acceleration or braking, due to the low coefficient of adhesion or friction, which typically exists between the steel wheel and the steel rail. The coefficient of adhesion of railroad wheels may be as low as 0.3 or less, which means that the pulling power of a towing vehicle is limited to a magnitude about 0.3 times the weight of the vehicle. To sustain loads greater than that amount, steel wheels will inherently slip on the track surface. For many years, sand has been a commonly used agent to increase the frictional characteristics of railroad wheels, but this technique only slightly enhances traction and produces only minimal benefits.
Recently, numerous attempts have been made to increase the adhesion coefficient of a steel wheel through chemical means, since sand only offers a partial solution to the slippage problem. Such chemical techniques often involve the treatment of metal surfaces with numerous materials which increase frictional contact between wheel and rail. Examples of chemical or metallurgical means to increase friction are disclosed in U.S. Pat. No. 2,877,716 to Ryznar and U.S. Pat. No. 4,310,191 to Halidin. Even though the incorporation of frictional materials into a wheel thread inherently increases frictional characteristics, this technique of solving the problem of wheel slippage has not attained ideal results. In the case of a rail wheel, a frictional material embedded in its periphey tends to abrade the steel rail. Further, it seems that a proper functioning frictional material advantageously should be composed of a matrix which sloughs the worn abrasive particles at the proper time in order to be effective. However, such programmed wearing away of the frictional material is simply not suitable in a railroad environment.
Efforts have been made in the prior art to reduce slippage of a vehicle wheel by a host of other techniques, including the employment of rigidly or resiliently mounted lugs, spikes or feet of various types that are constantly driven in contact with the wheel bearing support surface. The constant contact of devices with the road is an obvious disadvantage due to inefficiency of vehicle operation and the like. Further, with regard to the devices digging into the ice, snow, sand, earth or other soft surfaces, the traction is not attained, strictly speaking, by friction. In addition, where friction is involved, these devices only increase frictional contact in accordance with the force exerted by the springs or various devices. Accordingly, no satisfactory technique has been developed by which the adhesion characteristics of a vehicle wheel, whether a steel rail wheel, a pneumatic tire, and the like, can be enhanced for greater traction during acceleration and braking of a vehicle under a wide range of loading conditions.